This invention relates to a connector (for example, an antenna plug for an automobile) including an electrically-conductive plug pin functioning as a center contact, an insulating housing of an insulative nature fixed to an outer side of the plug pin, and an electrically-conductive outer contact fixed to an outer side of the insulating housing.
A related connector is disclosed in JP-A-2004-200019. In FIGS. 8 and 9, the connector 101, used for example as an automotive antenna plug, comprises an electrically-conductive plug pin 102 functioning as a center contact, an insulating housing 103 of an insulative nature fixed to an outer side of the plug pin 102, and an electrically-conductive outer contact 104 fixed to an outer side of the insulating housing 103. The connector 101 is designed to be electrically connected to an end portion of a coaxial cable 105.
The coaxial cable 105 comprises a center conductor 106 serving as a core wire, an insulator (not shown) serving as a dielectric, a braided conductor 107 serving as an outer conductor, and an insulating sheath 108 serving as an outer covering.
Here, the structure of the connector 101 will be briefly described with reference to its assembling procedure. In FIG. 10, the plug pin 102 is press-fitted into a pin insertion hole 109 of the insulating housing 103 from a front end side thereof as indicated by arrow P. At this time, this press-fitting operation is carried out while an engagement notch 110 of the plug pin 102 is disposed in registry with an engagement rib 111 of the insulating housing 103. In FIG. 11, when a front end portion of the engagement rib 111 is brought into abutting engagement with a front end surface of the engagement notch 110, thereby positioning the plug pin 102 relative to the insulative housing 103, retaining projections 112 bite into the engagement rib 111. As a result, the plug pin 102 is fixed to the inner side of the insulating housing 103.
The insulating housing 103, having the plug pin 102 fixedly mounted therein, is inserted into the outer contact 104 from a front end side thereof as indicated by arrow Q. At this time, this inserting operation is carried out while engagement projecting tabs 113 of the outer contact 104 are disposed in registry with guide grooves of the insulating housing 103, respectively. When distal ends of the engagement projecting tabs 113 slide past engagement step portions 115 of the insulating housing 103, respectively, the engagement projecting tabs 113 are engaged respectively with the engagement step portions 115 as shown in FIG. 9. Also, a front end edge of a contact body 116 abuts against projections 117 of the insulating housing 103 as shown in FIG. 9. As a result, the outer contact 104 is fixed to the outer side of the insulating housing 103.
When the insulating housing 103, having the plug pin 102 fixedly mounted therein, is thus inserted into the outer contact 104, an inner surface of the contact body 116 of the outer contact 104 presses retaining beams 118 of the insulating housing 103, so that retaining claws 119 of the retaining beams 118 are moved inwardly as indicated by arrows R in FIG. 11. As a result, the retaining claws 119 are engaged respectively in retaining holes 120 of the plug pin 102, thereby fixing the plug pin 102 to the inner side of the insulating housing 103, as shown in FIG. 9.
As will be appreciated from the foregoing description, the fixing of the plug pin 102 to the insulating housing 103 is effected by the fixing structure (in which the retaining projections 112 are brought into biting engagement with the engagement rib 111 as a result of press-fitting of the plug pin 102 into the insulating housing 103) and the fixing structure in which the retaining claws 119 are brought into retaining engagement with the respective retaining holes 120 as a result of inserting of the insulating housing 103 into the outer contact 104.
Next, the connection of the connector 101 to the coaxial cable 105 will be described. In FIGS. 8 and 9, a connecting portion 121 of the connector 101 includes a first engaging contact piece portion 122 and second engaging contact piece portions 123. Each of the first and second engaging contact piece portion 122 and 123 is in the form of a strip-like piece portion, and these piece portions 122 and 123 are bent inwardly such that their distal end portions are fitted or engaged together as shown in FIG. 12. More specifically, the second engaging contact piece portions 123 jointly assume a bifurcated shape. The first engaging contact piece portion 122 is inserted between the second engaging contact piece portions 123. That portion of each of the second engaging contact piece portions 123, disposed adjacent to its distal end, is bent to form a recessed portion 124 for positioning the center conductor 106 of the coaxial cable 105.
In FIG. 9, the axial cable 105, having the exposed center conductor 106 and braided conductor 107, is inserted into the outer contact 104 from a proximal end side thereof, and the center conductor 106 is placed on the first engaging contact piece portion 122 and the second engaging contact piece portions 123.
After the center conductor 106 is thus placed on the first and second engaging contact piece portions 122 and 123, the braided conductor 107 is positioned between pressing projections 127 of a jig 126 inserted through a connection notch 125 in the insulating housing 103, as shown in FIG. 13. Then, in this condition, the jig 126 is pressed down. As a result of pressing-down of the jig 126, the first engaging contact piece portion 122 and each second engaging contact piece portion 123 are moved away from each other, and at the same time the center conductor 106 is pressed down to be guided into the recessed portions 124 of the second engaging contact piece portions 123.
When the jig 126 is removed upwardly, the first engaging contact piece portion 122 and the second engaging contact piece portions 123 tend to be restored into their respective original shapes because of their own resilient forces, so that the center conductor 106, received in the recessed portions 124, is held between the first engaging contact piece portion 122 and the second engaging contact piece portions 123 as shown in FIG. 13. Thus, the electrical connection between the center conductor 106 and the plug pin 102 is completed.
In this condition in which the electrical connection between the center conductor 106 and the plug pin 102 is completed, inner press-clamping piece portions 128 of the outer contact 104 are inserted between the insulator (not shown) and braided conductor 107 of the coaxial cable 105, and in this condition, when outer press-clamping piece portions 129 are press-fastened, the braided conductor 107 of the coaxial cable 105 is fixed to the outer contact 104, and therefore is electrically connected thereto. Then, when sheath press-clamping piece portions 130 of the outer contact 104 are press-fastened onto the insulating sheath 108 of the coaxial cable 105, the whole of the connecting-side end portion of the axial cable 105 is fixed to the outer contact 104.
Finally, a covering piece portion 131 of the outer contact 104 is bent inwardly to cover the upper side of the connecting portion 121 of the connector 101, thereby isolating the plug pin 102 from the exterior, thus completing the series of assembling operations of the connector 101.
Thereafter, when the connector 101, connected to the coaxial cable 105, is fitted into a mating connector (for example, an automotive antenna socket) (not shown), the plug pin 102 contacts a signal terminal of the mating connector, and also a plurality of resilient contact piece portions 132 of the outer contact 104 contact a grounding terminal of the mating connector. As a result, the electrical connection between the connector 101 and the mating connector is completed.
The connector 101 is of such a structure that the first engaging contact piece portion 122 and the second engaging contact piece portions 123 directly grip or hold the center conductor 106 of the coaxial cable 105 therebetween, and the electrical connection is effected by this gripping condition. The following structures other than this structure have been proposed. For example, in the case of connecting a coaxial cable having an electronic part provided at its center conductor, techniques, disclosed for example in JP-A-2004-55426, can be used.
JP-A-2004-55426 discloses the coaxial cable having the electronic part provided at its center conductor. This publication also discloses a structure of connecting the coaxial cable, having the electronic part at its center conductor, to a connector. JP-A-2004-55426 will be described in a little more detail. The electric part has a pair of leads, and one of the leads is connected by soldering to the center conductor. The other lead is connected by soldering to a plug pin of the connector.
Further, a structure, not employing soldering, is disclosed in JP-A-2004-55426. Namely, an electronic part has a pair of leads, and one of the leads is connected by press-clamping to a center conductor. The other lead is also connected by press-clamping to a plug pin of a connector.
According to the technique disclosed in JP-A-2004-200019, there is provided the structure in which the retaining claws 119 of the insulating housing 103 are retainingly engaged in the respective retaining holes 120 of the plug pin 102, thereby fixing the plug pin 102 to the insulating housing 103. Generally, in the retaining structure using the retaining claws 119 and the retaining holes 120, each retaining hole 120 is set to a size slightly larger than the size of the retaining claw 119, so that fitting play or backlash is provided therebetween. The fitting play is necessary for smoothly bringing each retaining claw 119 into retaining engagement with the retaining hole 120.
In this structure having the fitting play, the plug pin 102 is allowed to move. Therefore, there is encountered a problem that the pressure of contact of the plug pin with the center conductor 106 of the coaxial cable 105 can not be sufficiently increased. When the contact pressure can not be sufficiently increased, a contact resistance increases.
And besides, according to the technique disclosed in JP-A-2004-200019, there is provided the structure in which the center conductor 106 of the coaxial cable 105 is gripped by the first engaging contact piece portion 122 and the second engaging contact piece portions 123 of the connector 101, thereby effecting the connection. Therefore, when the center conductor 106 can not be gripped by a sufficient gripping force, there is encountered a problem that the connecting reliability is lowered. Furthermore, the structure, having the first engaging contact piece portion 122 and the second engaging contact piece portions 123, is complicated as can be seen from FIGS. 12 and 13, and therefore this structure invites a problem that the productivity of the connector 101 is low.
On the other hand, in the technique disclosed in JP-A-2004-55426, the lead of the electronic part is connected to the plug pin by the connecting structure employing the soldering or the press-clamping. Therefore, in the case of the soldering, there is encountered a problem that the efficiency of the operation is very low. In the case of the press-clamping, there is encountered a problem that the reliability of connection of the lead to the plug pin is low (In the case where a single wire such as a lead is connected by press-clamping, it is difficult to obtain a proper press-clamped shape. Incidentally, in the case where a material of which the lead is made is harder than the plug pin, there are encountered problems such as a increased contact resistance value and a reduced adhering force.).